An 
emulsion comprising water as the continuous phase, a 
wax as the discontinuous phase, an emulsifier and a 
preservative having the general structure:  wherein R1 can be a heterocycle containing 
nitrogen and 
sulfur, such as thiazolyl, isothiazolyl, or thiadiazolyl, which can optionally be substituted with C1-C6 
alkyl; R2 can be 
hydrogen or C1-C6 
alkyl, specifically 
hydrogen; n is 0, 1, 2, or 3; each instance of R3 can independently be 
hydrogen, C1-C6 
alkyl, phenoxy, C1-C6 alkoxy, halo, amino, C1-C6 alkylamino, di C1-C6 alkyl amino, imidazolyl, thiazolyl, isothiazolyl, thiadiazolyl, thienyl, furyl, pyrryl, naphthyl, phenyl, halophenyl, C1-C6 alkyl phenyl, or C1-C6 alkoxyphenyl. The 
preservative may be added to the 
emulsion after the 
emulsion is formed. The emulsion can be incorporated into a 
gypsum product such as 
gypsum board or 
gypsum wood 
fiber board. The gypsum product may be made by forming a 
slurry containing gypsum, water, and the emulsion into a 
solid product. A method for improving the 
water resistance of a lignocellulosic composite product prepared by mixing lignocellulosic material with a binder to form a mixture and solidifying the mixture in a selected configuration to form the composite product may include adding to the mixture an emulsion as described above.